Here are some thoughts the current global financial crisis provoked, although I’ve thought about this on and off for years.
From Wikipedia, we have the basics of ecosystem services:
Humankind benefits from a multitude of resources and processes that are supplied by natural ecosystems. Collectively, these benefits are known as ecosystem services and include products like clean drinking water and processes such as the decomposition of wastes. Ecosystem services are distinct from other ecosystem products and functions because there is human demand for these natural assets. Services can be subdivided into five categories: provisioning such as the production of food and water; regulating, such as the control of climate and disease; supporting, such as nutrient cycles and crop pollination; cultural, such as spiritual and recreational benefits; and preserving, which includes guarding against uncertainty through the maintenance of diversity.
I propose that some things humans create for their own needs become system services, much like ecosystem services. These system services would be maintained in sustainable ways via application of the ProxThink Growth Model. We might start with energy provided in renewable ways. We might also try food, water, shelter, communication and community. The idea would be that when financial or market turbulence creates tight credit, or recessions come, the things that were system services would not become out of reach for people. When necessities become unattainable, personal and social troubles ensue.